Galaxy M51

M51 aka The Whirlpool Galaxy is an spiral galaxy that is estimated to be 23 light-years from the Milky Way Galaxy in the constellation Canes Venatici. It is one of the most famous galaxies in the sky.
The galaxy and its companion (NGC 5195) are easily observed by amateur astronomers. The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions.
It was discovered on October 13, 1773 by Charles Messier and designated as M51. Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain. It was however not until 1845 that the Whirlpool became the first to be recognized as a spiral. This was achieved by Lord Rosse.